The objective of this project is to synthesize a series of semisynthetic bleomycins which contain a strong chelating group (DTPA) attached to the bleomycin nucleus-bleomycinic acid. The chelation of a metallic gamma emitting radioisotope will then allow measurement of the distribution and rate of accumulation of the semisynthetic bleomycin by external detection. The chelation of the metal to a strong chelating group bound to the tumor seeking bleomycin should produce a diagnostic agent with ideal physical and chemical properties by permitting the use of the best available radioisotope 99m Tc. With the synthesis of these new compounds, the labeled antibiotic will not be limited by use of the isotopes of poor physical properties but strongly chelated (eg., presently used Co57) nor isotopes of good physical properties but weakly chelated (e.g., presently used In111).